colour fluctuation

Hi folks,
I was shooting some auditions yesterday (Canon XL-2) in a company boardroom, natural light supplemented by over head floresants.

Playing back the footage today, the first few takes look great, but the last half dozen or so the recorded image slowly fluctuates from just enough colour not to be monochrome to just under over saturation.

Have I pressed the wrong button somewhere to take it of the auto settings?
White balance was set to auto. My confusion comes from the fact the first few takes were fine, but the later ones all share this 'affliction'.

It doesn't sound like a white balance problem. Yes, you were recording under mixed lighting (natural light supplemented by over head flourescents) and this would give a colour cast of the opposite colour depending on which lighting was the more dominant, are you trying to describe a colour cast? Either shoot with the curtains/drapes closed to keep out the daylight or switch off the artificial lights instead.

Fluorescent lights can be very unpredictable and scary to work with, the ones they use in kitchens and offices anyway. Professional ones are more friendly.

Your problem could be a mixture of this and (but probably more related to) the sun.

Here you have two different types of light source with two different colour temperatures mixing together, at the same time the sun is on the move and adjusting that mix as it goes.

Different camera's have better automatic white balance controls than others. In general you want to use colour temperature correction filters on the lights to balance the colour temperatures of different type sources.

Some cameras can often get a good white balance under mixed sources in certain conditions. When you turn on your camera it automatically gets it's white balance related to light at that moment, it then stays there Then the sun moves. As it moves it adjusts the mix of fluorescent light and sun light to a level that doesn't match your camera's previously calculated white balance level.

You mention that the natural light was supplemented by the fluorescents. I am assuming here that neither the natural light or the fluorescents on there own weren't enough. In this case you need to look into colour temperature correction filters. Either cover the windows with sheets of the correct filter to match the fluorescents or cover the fluorescents with the correct filter to match the sun......

Another alternative is to turn off the fluorescents, they can be a nightmare to work with anyway. Get in a tungsten lamp or two, or even better three, and put sheets of the correct colour temperature correction filter over these to balance these with sun light. (CTB your looking for under these circumstances).

This way as the sun moves it's changing the mixture of two matching sources, the change in light conditions (the moving sun) has to be more extreme before it effects your picture in the way it has.

It's a good idea to adjust your white balance now and again when working under uncontrolled conditions.

No problem hope it turns out to be your problem right enough and you can sort it.

If your using the tungsten set up alone (as in without CT filters) you'll probably want to close the curtains or your light will just mix again. It will be a more stable mix than previously due to one of the sources having become a stable source but the natural sky still isn't that stable. Especially with the clouds, which may have been your 20 seconds thing.